While working on #180, I wanted to throw weeder at the project, to see if we could get some quick wins. While doing that, I have edited the ghc-options section of our stack.yaml with the recommended weeder settings, but I couldn't understand why stack wasn't picking them up.

It turns out that we have two ghc-options sections in our stack.yaml: one here and one here. I think that's happening is that stack is considering only the latest it encounters. After I have placed the relevant weeder settings in the last section, it worked.

Regardless of stack's behaviour, we should probably unify them, as it's confusing and error prone to have two ghc-options entries. This also means that it's likely that this currently not being enforced by stack:

ghc-options:
  "$everything": -fprint-potential-instances